1. Field of the Invention
This invention relates to improvements in a cationic electrodeposition paint composition, and more particularly to a cationic electrodeposition paint composition which is high in an ability for covering an edge portion of a metal plate and high in weatherability.
2. Description of the Prior Art
Hitherto a cationic electrodeposition paint has been prepared by neutralizing a variety of basic resins such as basic epoxy resin, acrylic resin and polyurethane resin with organic, acids and thereafter diluted with water. In order to accomplish an electrodeposition painting, a metal object to be coated with a paint is dipped in the cationic electrodeposition paint and serves as a cathode. Upon passing direct current through the metal object, a paint film is deposited on the surface of the metal object and thereafter baked to be hardened.
It is usual to use the cationic electrodeposition paint including epoxy resin as a main component. Such a cationic electrodeposition paint including epoxy resin is excellent in corrosion resistance of the metal object (plate) to be coated with the paint but is inferior in weatherability. In contrast, another cationic electrodeposition paint including acrylic resin as a main component is excellent in weatherability but inferior in the corrosion resistance of a metal object (plate) coated with the paint. Such a fact is well known in the art.
Additionally, in recent years, an improved cationic electrodeposition paint including epoxy resin as a main component has been proposed to raise an ability of covering an edge portion of a metal plate. Such electrodeposition paints are disclosed for example in Japanese Patent Provisional Publication Nos. 58-204065, 61-293273, 63-266097 and 62-174277.